Only Render Vertexes with Normals Parrallel to the Screen?
I would talk of poligons (faces), as vertex can't be strictly said "renderable": they are 0-dimensional (you'll need for example to use a halo materal to create something around the vertex).
What we see rendered/drawn in the 3D Viewport is a also a rapresentation, a placeholder, built to make them visible.



You can filter out the faces in a "static" way by select one of the faces whose normal is pointing toward the camera and then:

 Select -&gt; Select Similar -&gt; Normal




The thereshold value would act as the "tollerance" factor you mention. Repeat also for the backfaces. Once selected  both you can delete them, or separate them and tweak visibility, assing a different material, or even assing them to a vertex group and use the Mask modifier.



Or you can work with materials to obtain a dynamic masking.

In cycles there is the Layer Weight node whose Facing options is able to assing a factor to the faces based on how much their normals are pointing toward the camera



The factor can be used to mix a shader with a Transparent shader:



By tweaking the Color Ramp's handles you'll have full control on the masking range, not just a tollerance.

Notice that this way you are rendering all the faces (some are trasparent and some not, but the path tracing takes all in account). The static way previusly exposed will probably render faster, as it excludes faces from the caluculation, while the dynamic doesn't.